Effect of different concentrations of sulfuric acid on leaching of radionuclide isotopes in sedimentary rock samples,Sinai, Egypt

Journal of Radioanalytical and Nuclear Chemistry - This research focused on studying the effect of sulfuric acid concentrations on the leaching of different radionuclides (238U and 235U series) in...     

Nuclear excitation by positron annihilation with bound electrons in a screened atomic potential

We have calculated the total cross section for the process of nuclear excitation in positron-bound electron annihilation. The calculations presented in this work use a spherically symmetric screened atomic potential. Comparisons with more approximate treatments of the process are made.     

Separation and fluorodensitometric determination of some purine derivative drugs by thin-layer chromatography on starch and cellulose

Summary Purine derivative drugs, aminophylline, theophylline, xantinolnicotinate, 6-mercaptopurine, 6-thyoguanine, azathioprine, 1-methylxantine, 3-methylxantine, 1-methyluric acid, 1,3-dimethyluric acid, 6-thioxantine, 2-amino-6-methylmercaptopurine, were separated by thin-layer chromatography on rice starch and cellulose by three different solvent systems. Conditions for quantitative fluorodensitometric determination of purine derivatives drugs were investigated.     

Structural and vibrational properties of tetraoxaporphyrin dication, the oxygen analogue of porphyrin, and of isoelectronic diprotonated porphyrin

Structural calculations by means of the density functional method have been performed on tetraoxaporphyrin dication and on isoelectronic diprotonated porphyrin as well as on the sulfur and carbon analogues of porphyrin. A detailed study of the stable conformations of these compounds is reported starting with the most symmetrical conformations and lowering the symmetry along the vibrational coordinates with imaginary frequency. The calculated geometries are related to experimental structures available from X-ray diffraction studies. The Raman spectra of tetraoxaporphyrin dication exciting with micro-Raman instrumentation at 785 nm and of diprotonated porphyrin in near-resonance conditions with the Soret band have been measured. The correlation between frequencies calculated with the DF/B3-LYP/cc-pVDZ procedure for porphyrin, diprotonated porphyrin, and tetraoxaporphyrin dication has allowed for making a vibrational assignment for the latter two systems in excellent agreement with experiment using a single frequency scale factor.     

The thermal behaviour of lignins from wasted black pulping liquors

The thermal degradation of lignins separated from black liquor waste from pulping of bagasse and cotton stalks has been investigated. Thermal gravimetric analysis (TGA), differential thermal analysis (DTA) and derivative thermogravimetry (DTG), between 20 and 1000°C, have been used. Activation energies of treated lignins were calculated. Lignins separated from liquors obtained at low pulping temperature have higher activation energies than high-temperature lignins. The use of anthraquinone (AQ) as an additive for accelerating the pulping process raises the activation energy of the lignin in the black liquors waste.     

Stereoselectivity of 1,3-dipolar cycloadditions of l-valine-derived nitrones with methyl acrylate

Chiral nitrones derived from l-valine react with methyl acrylate to afford the corresponding diastereomeric 3,5-disubstituted isoxazolidines. The dibenzylsubstituted nitrone gave also 3,4-disubstituted isoxazolidine in 4% yield, additionally. The stereoselectivity was dependent on the steric hindrance of the nitrone and reaction conditions. High pressure decreased the reaction time of the cycloadditions. The major products were found to have the C-3/C-6 erythro and C-3/C-5 trans relative configuration. The major cycloadduct undergoes N-O cleavage and deprotection to a chiral diaminodiol derivative.     

O/O and H/D separation factors for liquid/vapor permeation of water through an hydrophobic membrane

Liquid/vapor permeation of water through commercial grade hydrophobic PTFE membranes at 323<P(Torr)<160, shows enhancements in logarithmic separation factors, ln[(i'/i)] = In [(χ'/χ) _downstream/ (χ'/χ) _upstream], which differ markedly for isotope separation of oxygen and hydrogen. The prime refers to the lighter isotope and χ is the mole fraction. Thus ln[(16/18)] is found to be as large as 6 times the ratio of the vapor pressure isotope effect, ln(_o = ln (P^o'/P^o), but ln[(H/D)]/ln[_o(H/D)] is only as large as 1.3. The difference in enhancement factors indicates that membrane transport mechanisms must be different for the two separations. The unusually large separation factor for ¹⁶O/¹⁸O may be of practical interest.     

A Review of HER4 (ErbB4) Kinase,Its Impact on Cancer,and Its Inhibitors

HER4 is a receptor tyrosine kinase that is required for the evolution of normal body systems such as cardiovascular, nervous, and endocrine systems, especially the mammary glands. It is activated through ligand binding and activates MAPKs and PI3K/AKT pathways. HER4 is commonly expressed in many human tissues, both adult and fetal. It is important to understand the role of HER4 in the treatment of many disorders. Many studies were also conducted on the role of HER4 in tumors and its tumor suppressor function. Mostly, overexpression of HER4 kinase results in cancer development. In the present article, we reviewed the structure, location, ligands, physiological functions of HER4, and its relationship to different cancer types. HER4 inhibitors reported mainly from 2016 to the present were reviewed as well.     

Unraveling orbital ordering in La0.5Sr1.5MnO4

Orbital ordering (OO) in the layered perovskite La0.5Sr1.5MnO4 has been investigated using the enhanced sensitivity of soft x-ray resonant diffraction at the Mn L edges. The energy dependence of an OO diffraction peak over the L(2,3) edges is compared to ligand-field calculations allowing a distinction between the influences of Jahn-Teller distortions and spin correlations. The energy dependence of the diffraction peak at the Mn L1 edge is remarkably different from that observed at the Mn K edge.     

Assembly and charge transfer in hybrid TiO(2) architectures using biotin-avidin as a connector

Exploiting the presence of undercoordinated surface Ti atoms at the tips of TiO2 nanorods and the dopamine selectivity for these Ti surface states, biotin was conjugated to TiO2 nanocrystallites using dopamine as a bridging linker. Using abiotin-avidin complex as a connector the "tip-to-tip" assembly of 400 nm elongated TiO2 rods was obtained. The photoexcitation of avidin-TiO2 hybrids resulted in the transfer of holes from nanocrystallites to protein and consequent oxidation of avidin, most probably at tyrosine 33.